The general aim of this project, now in its 11th year at the Beth Israel Hospital, Harvard Medical School, remains the conduct of an interdisciplinary and interdepartmental research on the pathophysiology of thrombosis and atherosclerosis. The long range goals of the program are several. One major goal is the understanding of the factors that initiate and propagate thrombosis and appreciation of the systemic effects of thrombosis. A second goal is the study of the factors that control vascular tone and initiate hypertension. The Program Project is composed of 14 projects and three core facilities drawn from the Departments of Medicine, Surgery, Pathology and Radiology.